The present invention relates to anchoring devices for fixing structural cables to building elements.
In particular, the invention applies each time it is necessary to fix a cable, subjected to tensile loadings, to equip building elements such as cable-stayed bridges, suspension bridges or the like, by connecting the tops of the towers of these bridges to their decks and to their anchor blocks.
The cables habitually encountered in such building elements comprise a number of strands each of which comprises metal wires themselves enveloped together in a protective sheath, each of these protective sheaths being interrupted at a terminal edge so that the strands each have a bared end portion.
The anchoring devices habitually encountered, particularly in EP-A-0 323 285, comprise:
a perforated block in which the bared end portions of the various strands are individually anchored,
a bearing surface which is secured to the building element and against which the periphery of the perforated block axially bears,
a tube to which the perforated block is attached on the bearing surface side, the tube transversely delimiting a chamber inside which the terminal edges of the strands are located and which is filled with a substance that protects the bared end portions present in the chamber, and
a packing box which seals the chamber, at the opposite end to the anchoring block, and which has the sheathed strands passing in a sealed manner through it, the packing box comprising:
at least two perforated plates of which one, known as the inner plate, is arranged on the same side as the chamber and of which the other, known as the outer plate, is arranged at the opposite end to the perforated block with respect to the inner plate, and
at least one piece of packing which is inserted between the inner plate and the outer plate.
In the known embodiments of the packing boxes encountered in the anchoring devices of the kind in question, the inner plate of the packing box is stationary while the outer plate can move and is driven toward the stationary plate by means of threaded rods passing through the perforated block and placed under tension. These rods are both screwed into the outer plate and into a nut butting against the perforated block.
To ensure good leaktightness of the anchoring device, it is possible for the packing of the packing box to be compressed again by exerting tension on the outer plate should that prove necessary. However, the ends of the threaded rods screwed into the outer plate are located on the same side as the cables and are therefore not accessible to the operator unless he dismantles the entire anchoring device.
An anchoring device such as this therefore involves significant and expensive maintenance operations because the mechanically stressed parts are located in places which are difficult to access.
It is an object of the present invention to overcome the aforementioned drawbacks by providing an anchoring device that makes maintenance operations easier.
To this end, according to the invention, an anchoring device of the kind in question is essentially characterized in that the outer plate is stationary with respect to the chamber and in that the device comprises means for pressing on the inner plate.
Thus, by virtue of these arrangements, all the constituent elements of the packing box are protected against corrosion and the elements which allow the packing to be compressed are accessible from the opposite side of the anchoring device to the side from which the cables extend, and therefore do not entail costly disassembly.
In some preferred embodiments of the anchoring device according to the present invention, recourse is further had to one and/or other of the following arrangements:
the means for pressing on the inner plate comprise a compression rod, one end of which is in abutment against the inner plate and the other end of which passes through a hole made in the perforated block and which can be actuated from the opposite side of the perforated block to the bearing surface secured to the building element;
the compression rod is a threaded rod and the hole is tapped, the rod being operable by screwing;
the compression rod is in abutment against an insert plate fitted adjacent to the inner plate;
the pressing means comprise a stop which is integral with the tube and which is situated inside the tube at a distance from the outer face of the outer plate that is more or less equal to the thickness of the packing box, and in which said at least one piece of packing is perforated with passages of a diameter smaller than the diameter of the sheathed strands;
the packing box is placed in a groove formed inside the tube and the stop is defined by the step between the groove and the main part of the tube;
the outer plate is in abutment against a stop sleeve attached to the end of the tube by screwing;
the outer plate is in abutment against a perforated plate attached to the end of the tube;
the protective substance is compressed in the chamber; and
a cap is sealed onto the perforated block, delimiting a chamber into which the bared end portions of the strands project, the chamber being filled with said protective substance.